I don't want to sidetrack this thread (I'm very interested because I have sound issues on a Meteor I just acquired) but I have a question about the wiring for the mpu A4J3. My switches all register correctly in test mode. The coils, however, don't fire correctly. I've verified the coils are good (going to ground each coil fires just fine). I have studied the switch matrix wiring and I think whoever had this before has it wired up incorrectly. For instance, firing the pop bumper causes the M drop target to drop. Other coils won't fire at all. Right slingshot switch causes one of the drop target banks to reset. Just all messed up.
Can you please (oh please) take a photo of A4J3 wiring and identify all the wire colors and pin location?
Thanks!!!

Thanks Ralph67, for the pic. All my wiring connections look to be correct. I'm having a very similar coil firing problem like Brian.
I'm just starting on this Meteor. Just starting to get it operational. This is a project machine. I put in a new Alltek mpu and solenoid driver board. The original lamp driver has 2 tips that need to be replaced but that can wait. I don't get all the sounds out of the sound board. Unplugged for now. The switches are very dirty, but I can get them to pass the switch test wiggling them around. I'm going to clean them up and repin the dirty connectors for J2 on the solenoid driver board (A3J2). Could the dirty switches and dirty A3J2 connector be causing the switch matrix to get bad data?
And on the mpu, I have the dip switches set for Stern clock speed. I did a memory clear and have the game set for meteor.
In coil test, not all the coils fire. The meteor drop targets 6, 8, 9 and 10 fire instead of some of the other coils in testing.
What does work is left bottom drop target bank, left top target bank, flippers, out-hole, coin lock-out.

In game play:
Close right sling switch: O drop target fires
Close left sling shot switch: Top left drop target resets
Close pop bumper switch: M drop target fires
Closing all switches on meteor drop target: Outhole coil fires

This thing is possessed.
Does anyone see a pattern here that I'm missing? I hope it's just filth and the pending clean-up will fix it.

Thanks Quench for the great suggestions! I repined A4J4, A3J2 and A3J4 connectors. Now all the coils fire correctly!
Tomorrow I'll move to the cleanup stage. Lots of work to do there.
Now, about the sound issue. At the end of the game I get a scratchy rocket sound but that's it. The same sounds come up in the solenoid test. I checked out a youtube video to see what all kinds of sounds there are. But other than the rocket, I get nothing.
I'm not sure how to approach the sound board. Suggestions?

Got my sound working! Last night I brought the ribbon cables in and checked for continuity on each pin. Pin 1 was broken. So, I repaired that and tested this morning. All sounds are working! So, the restoration continues. I've rebuilt three drop target banks and am half way through the meteor drop target bank. It's starting to take shape!